In medical diagnostic ultrasound harmonic imaging, acoustic energy is transmitted at a fundamental frequency. Echoes generated by propagation and/or reflections at a harmonic of the transmitted frequency are received. For example, a transducer generates acoustic energy in a band of frequencies centered at 2 MHz. The same transducer is used to receive the echo signals at a harmonic band of frequencies centered at the second harmonic of 4 MHz. The transducer may have a limited bandwidth, so the harmonic signals are positioned at a high end of the bandwidth. Given this bandwidth limitation, the received signals are generally narrow-band and may have weaker signal strength.